This invention relates to a shunt valve for draining of cerebrospinal fluid.
In the treatment of hydrocephalus, it has been customary to drain excess cerebrospinal fluid (CSF) from one site in the body to another. For example, a catheter may be introduced into the ventricle within the brain and connected through a pressure operated check valve to a subcutaneous catheter so that the CSF is introduced into the blood stream or the peritoneal cavity. Alternatively, a catheter may be inserted into the body adjacent the spine and connected through a check valve to a catheter inserted in the peritoneal cavity. The latter is commonly termed a lumbar peritoneal shunt system and may be employed only upon patients afflicted with communicating hydrocephalus in which the excess CSF is not confined to the cranium, but is present in the region of the spine.
The invention of the first functioning hydrocephalus shunt was made in 1956 as disclosed in U.S. Pat. No. 2,969,066 (Holter). Numerous improvements and changes were made to this invention as described in further detail below. However, problems such as overdrainage of CSF continues to be a major cause of shunt malfunction and revision.
Shunt systems of this general sort are disclosed in U.S. Pat. Nos. 3,288,142 (Hakim) and 3,527,226 (Hakim). These shunt systems do not satisfactorily solve a problem brought about by the pressure drop which results when the patient shifts from a substantially horizontal to a substantially vertical position. The check valves normally include a spring action to keep the valves closed until the CSF pressure rises to a predetermined pressure setting of the valve. However, in the case of a patient fitted with a lumbar peritoneal shunt system, the hydrostatic head, working upon the check valve, increases abruptly when he moves from a horizontal to vertical position, and the pressure increase causes the valve to open. The result is excessive rate of drainage. The similar rate of drainage change is caused by the length of the drainage tubing on a ventriculo atrial or ventriculo peritoneal shunt system as the patient moves from horizontal to vertical.
In 1976, in an attempt to minimize the risk of overdrainage, U.S. Pat. No. 3,991,768 (Portnoy) issued that was directed to an anti-siphon device to control the flow of CSF which occurs when a patient rises from a supine position. Here, the shunt system drains fluid from one region of the human body and discharges it into another in which means is included to resist overdrainage or siphoning of the region as a consequence of low downstream hydrostatic pressures. The system includes a collector catheter and a discharge catheter, and a valve that interconnects these catheters to open the system to flow, or to close it to flow, as a consequence of the position of its closure means which is responsive to the pressure differential between the pressure in the valve as transmitted by the catheters, and a reference pressure such as the atmosphere. The concept behind this device was that maintaining the pressure at a constant, positive value minimizes the risk of overdrainage and the complications that result. The anti-siphon device maintained the differential pressure across the valve close to atmospheric pressure, suppressing the hydrostatic column that forms in the distal catheter when the patient stands.
U.S. Pat. No. 4,795,437 (Schulte et al.) modifies the invention of Portnoy and discloses a subcutaneously implantable siphon control device for use in a shunt system. The device includes a proximal catheter, a flow control valve and a distal catheter. The siphon control device limits fluid flow through the shunt system due to the siphoning effect of negative hydrostatic pressure created by the elevation of the proximal catheter inlet with respect to the distal catheter outlet. The siphon control device includes a base having an inlet placed in fluid communication with an outlet of the flow control valve, and an outlet placed in fluid communication with the distal catheter, and a housing for the base which, in connection with the base, defines a fluid flow pathway between the inlet and the outlet. The base provides a wall having substantially parallel upper and lower seating surfaces, which separates the inlet from the outlet. A pair of spaced, substantially parallel, flexible and elastic diaphragms having inner and outer surfaces are provided by the housing, and are situated on opposite sides of the wall to position a portion of each inner surface in contact with an adjacent one of the seating surfaces. Unfortunately, a high rate of complications due to both under and over drainage still occurred with the use of an anti-siphon device. In addition, the anti-siphon device introduced the entirely new complication of occlusion due to tissue encapsulation.
Subsequently, in 2000, U.S. Pat. No. 6,090,062 (Sood et al.) issued which discloses a programmable anti-siphon device which, while still susceptible to tissue encapsulation, incorporates a feature which permits the relationship between the seat and membrane to be adjusted to compensate for tissue encapsulation or increased or decreased levels of anti-siphon pressure.
In 2002, U.S. Pat. No. 6,383,160 (Madsen) disclosed a variable anti-siphon device for use in cerebrospinal fluid shunt systems. The devices include a housing with an internal chamber, an adjustable barrier separating the chamber into two cavities, and a diaphragm that seats itself against the adjustable barrier with a seating force that is proportional to the pressure differential across it. The adjustable barrier allows the level of anti-siphon protection to be modified. In one embodiment, the height of the adjustable barrier may be varied. In another embodiment, the barrier is moved longitudinally within the internal chamber to vary the volume of each chamber. This device modifies the invention of U.S. Pat. No. 6,090,062 (Sood et al.) by permitting non-invasive adjustment.
The above designs suffer from several problems. First, they depend upon an elastomeric membrane, which, by virtue of the properties of elastomers, tend to increase in stiffness over time, thereby changing the functional properties of the membrane. Additionally, these pressure sensitive membranes are in contact with surrounding tissue and may be pressed upon by scar tissue, encapsulating the mechanism, thereby increasing the pressure necessary to overcome the encapsulation. Furthermore, these devices are generally implanted on the cranium under the scalp, and may be occluded by the weight of the skull resting on the device when the patient is recumbent. Finally, in order for these devices to be sufficiently sensitive to changes in pressure, the membranes must be very thin and delicate. They may be easily damaged or destroyed by puncture with a needle, which may occur whenever CSF samples are taken or medication is administered through the shunt.
U.S. Pat. No. 3,889,687 (Harris et al.) discloses a shunt system for the transport of cerebrospinal fluid that compensates for overdrainage by the use of a gravity and attitude activated device consisting of a pressure valve mechanism and separate multiple ball-in-cylinder design. When properly implanted with the axial dimension of the valve cylinder parallel to the vertical axis of the patient, the balls are free to move within the cylinder and the intracranial pressure (ICP) is controlled by the pressure valve. Here, when the patient rises from the recumbent to the standing or sitting position, placing the ball and cylinder in the vertical position, the balls bias against the inlet of the cylinder and the weight of the balls increase the system pressure to prevent over drainage. Unfortunately, this device is bulky and highly position sensitive, and only works properly in the vertical position. This design was designed to be implanted on the patient's side, above the waist, at the level of entry of the lumbar catheter into the spine, to be used with a lumbar catheter for drainage of CSF from the lumbar space. An additional problem was that the cylinder and balls, as well as the differential valve mechanism, were made of stainless steel, which causes an artifact on CT or MRI imaging. This is especially troublesome, as lumbar catheter placement leads to a higher complication rate of spine problems, thereby necessitating imaging of the exact area which is compromised by the magnetic implant.
U.S. Pat. No. 5,042,974 (Agarwal) discloses a shunt valve for draining cerebrospinal fluid. The shunt valve includes a deformable housing having a proximal and distal end. A non-deformable valve chamber is disposed within the housing to form an inlet chamber with the distal end and an outlet chamber with the proximal end. The shunt valve has an inlet into the inlet chamber and an outlet from the outlet chamber. The flow of the fluid within the shunt valve is a Z-flow path and the inlet and outlet are provided along the same axis. This design modifies the design of the Harris '687 patent discussed above. Here, the valve mechanism is eliminated thereby reducing the size and bulk such that the device is suitable for placement under the scalp next to the posterior portion of the cranium, such that it is parallel to the vertical axis of the patient when the patient is standing or sitting. However, to function properly as a shunt, the device must be used in conjunction with an anti-reflux mechanism. Additionally, this device was manufactured from stainless steel thereby compromising CT and MRI images.
U.S. Pat. No. 3,769,982 (Schulte et al.) is directed to a physiological drainage system with closure means responsive to downstream suction. The system is for draining liquids from a source of the human body to a region where it is disposed of. The latter region is at a different elevation from the source region. The system is provided with a control which is responsive to downstream suction. When the suction is excessive, the control closes the system to flow so as to prevent over-drainage of the source region. The control comprises a valve which remains open to flow at normal rates and downstream suction levels, and which closes when the downstream suction level is above a predetermined level.
U.S. Pat. No. 4,621,654 (Holter) is directed to an attitude and pressure responsive valve assembly. This valve assembly is for relieving intracraneal pressure and includes a valve housing adapted for implantation and having an inlet port for connection to a ventricular catheter and an outlet port for connection to a venous or peritoneal catheter. The valve housing includes a fluid passage, the flow through which is controlled by a first pressure sensitive valve of relatively high resistance and a second pressure responsive valve of relatively low resistance. An attitude responsive valve is disposed in the fluid passage in parallel with the first pressure responsive valve. The valve assembly is implanted in a patient with the attitude responsive valve in a closed position when the patient is in an upright position and in an open position when the patient is in a horizontal position. The employment of pressure responsive and attitude responsive valves in parallel provides ventricular pressure relief regardless of the patient's position.
U.S. Pat. No. 4,443,214 (Marion) discloses a valve adapted to be inserted between a ventricular catheter and a draining catheter and comprises a body of a flattened cylindrical shape enclosing a chamber having formed through its cylindrical wall an inlet passage for introducing the cephalorachidian fluid and an outlet passage for discharging this fluid. At the inner end of the inlet passage, a frustoconical seat engageable by a ball valve acting as a non-return valve is provided. This ball valve is urged against the seat by a curved spring blade extending along the lateral inner wall of the chamber and is mounted in overhanging relationship on a diameter bar of magnetic material mounted in turn for concentric rotation on a pivot pin extending across the chamber. A tooth carried by the bar end opposite the spring blade engages detent-positioning dents formed in the lateral wall of the chamber.
U.S. Pat. No. 4,595,390 (Hakim et al.) discloses a surgically-implantable shunt valve for venting CSF in the treatment of hydrocephalus in which popping (pulsing) pressure is adjusted in finite increments by application of an external magnetic field.
U.S. Pat. No. 4,615,691 (Hakim et al.) discloses a surgically implantable stepping motor isolated physically from electrical power sources and powered by a magnetic field applied from outside the apparatus.
U.S. Pat. No. 6,126,628 (Nissels) discloses a device for limiting the flow of a fluid from a first region of a patient's body to a second region. The device includes a primary passage for directing fluid from an inlet of the device to an outlet in response to the fluid flow rate being less than a predetermined level and a secondary passage for directing fluid from the inlet to the outlet in response to the flow rate being greater than or equal to the predetermined level. The secondary passage is a tortuous flow path and presents a higher resistance to fluid flow than the primary passage. A detector closes the primary passage in response to the flow rate reaching the predetermined level in order to force the fluid to pass through the secondary passage. When the fluid flow rate reaches overdrainage, the fluid is forced through the secondary passage in order to effectively reduce the fluid flow rate and prevent overdrainage. As soon as the flow rate decreases below the predetermined level, the primary passage opens itself automatically.
U.S. Pat. No. 3,111,125 (Schulte) discloses a drainage device that includes a diaphragm-type pump and a conduit to form shunt connections with various parts of the human body to relieve one of the parts of undesirable accumulations of fluids.
U.S. Pat. No. 4,787,887 (Saenz Arroyo) discloses a ventricular by-pass device for draining the cephalorachidian liquid in the hydrocephalus. It consists of a check valve device which obstructs the brain suction orifice. Its valve controls the flow of fluid in the shunt system according to the differences in pressure at a point inside the valve and the pressure in a bodily region outside and near the valve.
U.S. Pat. No. 5,643,195 (Drevet et al.) discloses a device for regulating the flow of an organic liquid between a production site and a resorption site of a patient in a drainage circuit that extends between the two sites where one of the sites is a site of small pressure variation and the other is a site of large pressure variation. Pressure is regulated particularly as a function of the position of the patient.
All references cited herein are fully incorporated herein by reference in their entireties.